1. Field of the Invention
The present invention relates to a method for manufacturing a semiconductor device and more particularly, to a method for dry etching an insulating layer using a novel plasma.
2. Description of the Related Art
Highly integrated semiconductor devices with a capacity of 256 M or higher require intricate process steps to achieve the desired performance threshold. One such process involves etching a silicon oxide layer in order to form a small and deep contact having a high aspect ratio. Furthermore, to increase the integration density, a self aligned contact (SAC) process is implemented as well. For each of these processes, a high selectivity ratio is an important requirement.
A gas from the fluorocarbon (CxFy)-series is generally used in etching silicon oxide. For example, a gas having a high ratio of carbon to fluorine, such as C3F8 or C4F8, is used in the etching process. Moreover, to increase the selectivity ratio, a gas from the hydroflurocarbon (CxHyFz)-series is added to the fluorocarbon gases. Furthermore, when dry etching a silicon oxide at a high selectivity ratio, oxygen and oxygen-containing gases such as carbon monoxide (CO) must be added to C4F8 gas. The oxygen or carbon monoxide is added for preventing etch stopping or for controlling the profile of a contact hole to be formed.
Of course, in order to add oxygen gas, a process of controlling the supply of oxygen gas must be employed. Thus, it becomes more complicated to control the overall process of dry etching. Likewise, it is necessary to separately install a gas supply system in the etching equipment to deliver the oxygen gas, which makes the structure of the etching equipment more intricate.
To solve the above problems, it is a feature of the present invention to provide a method for etching an insulating layer in a semiconductor device with a novel etching reactive gas, which novel etching reaction gas replaces the fluorocarbon (CxFy)-series gas.
Accordingly, to achieve the above feature, the present invention provides a method of etching an insulating layer, such as a silicon oxide layer or silicon nitride layer, on a semiconductor substrate by dry etching the insulating layer with a reactive gas containing Ar and C4HxF8-xO, wherein x is an integer from 0 to 4.
Preferably, the C4HxF8-xO gas is C4F8O, wherein x is 0. In this case, the reactive gas can be a mixed gas of C4F8O gas and C4HxF8-xO, wherein x is an integer from 1 to 4. The oxygen component of the reactive gas may be oxygen gas, or an oxygen-containing gas such as carbon monoxide or carbon dioxide. The reactive gas may further include CxFy gas, wherein x is an integer from 1 to 6, and y is an integer from 2 to 12. Furthermore, the reactive gas may include CXHyFz gas wherein x is an integer from 1 to 6, y is an integer from 1 to 4, and z is an integer from 2 to 10.